1. Field of the Invention
The invention relates to a scanning probe microscope for obtaining an observation image of a sample by using a physical phenomenon (for instance, a tunnel current or a force between atoms) which is observed when the probe approaches the sample and also relates to a method of observing the sample by using the scanning probe microscope.
2. Related Background Art
In recent years, there has been developed a scanning tunnel microscope (hereinafter, abbreviated to "STM") in which a probe and a sample are allowed to approach and electron structures of and near the material surface can be directly observed by using a tunnel phenomenon a physical phenomenon which occurs at this time (refer to G. Binning et al., "Helvetica Physica Acta", 55.726, 1982). A real spatial image can be measured at a high resolution irrespective of whether the sample is monocrystalline or amorphous. The STM also has an advantage in that the electron structures can be observed at low electric power without damaging the medium by a current. Further, the STM operates even in the atmosphere or in a solution as well as in an ultra-high vacuum and can be used for various materials. Applications in a wide range in the scientific or research field are expected. In the industrial field as well, in recent years, as disclosed in, for instance, JP-A-63-161552 and JP-A-63-161553, attention is paid to the principle that the STM has a spatial resolution of atomic or molecular size. Application to a recording and reproducing apparatus and the realization to put the STM into a practical use are vigorously being pursued.
Since the STM has a spatial resolution of molecular size, in the conventional STM apparatus, a stage or a probe causes a drift due to fluctuations of the temperature, vibrations, or influences of the driving system such as a piezoelectric actuator or the like, so that the probe scanning area on the sample surface is moved. Thus, there is a problem that an observation object moves with the lapse of time. Such a problem also occurs in other scanning probe microscopes, for example, an atomic force microscope (AFM).